This invention relates to an actuating mechanism. More particularly, this invention relates to an actuating mechanism which includes a thermal bend actuator.
The applicant has invented a page width printhead which is capable of generating text and images of a resolution as high as 1600 dpi.
The printheads are manufactured in accordance with a technique that is based on integrated circuit fabrication. An example of such a technique is that which is presently used for the fabrication of micro electromechanical systems.
These fabrication techniques allow the printhead to incorporate up to 84000 nozzle arrangements. The nozzle arrangements are electromechanically operated to achieve the ejection of ink.
In a number of the Applicant""s inventions, the nozzle arrangements incorporate thermally actuated devices which are displaceable within nozzle chambers to eject the ink from the nozzle chambers. Many of the thermal actuators use a combination of materials and a bending action which results upon an uneven expansion of the materials. The thermal actuators are manufactured by depositing consecutive layers of material having different coefficients of thermal expansion.
The present invention was conceived to address certain problems associated with such actuators. A significant problem with such actuators is that the different materials can result in bending and bending stresses being set up in the thermal actuator when the thermal actuator is inoperative and exposed to transient conditions. As is known in the field of integrated circuit fabrication, the deposition of material results in a heating of both the material being deposited and the material on which the deposition takes place. The fact that the materials have different coefficients of thermal expansion can result in the bending of the laminated structure upon cooling. Those skilled in the field of micro electromechanical systems fabrication will appreciate that this is highly undesirable.
According to the invention, there is provided an actuating mechanism which comprises
a thermal bend actuator having a laminated structure of at least three layers in the form of a pair of opposed, outer layers and at least one inner layer, wherein
the outer layers are of substantially the same material and of substantially the same dimensions.
The invention also relates to an ink jet printhead which comprises
a substrate; and
at least one nozzle arrangement formed on the substrate, the, or each, nozzle arrangement defining a nozzle chamber and having an ink ejection mechanism for ejecting ink from the nozzle chamber, wherein
the ink ejection mechanism includes an actuating mechanism which comprises a thermal bend actuator having a laminated structure of at least three layers in the form of a pair of opposed, outer layers and at least one inner layer, wherein
the outer layers are of substantially the same material and of substantially the same dimensions.